Webster's New World Medical Dictionary

metatarsal
One of the five cylindrical bones that
extend from the heel to the toes.
methadone
A synthetic opiate. The most com-
mon medical use for methadone is as a legal substi-
tute for heroin in treatment programs for drug
addiction.
methemoglobin
A form of hemoglobin that is
incapable of carrying oxygen, sometimes found in
the blood after certain poisonings, such as with ani-
line, nitrates, and other compounds.
methicillin-resistant Staphylococcus aureus
Staphylococcus aureus (a type of staph bacteria)
resistant to the antibiotic methicillin. Abbreviated
MRSA. MRSA first appeared among people in hospi-
tals and other health facilities, especially among the
elderly, the very sick, and those with an open
wound, an IV catheter, or a urinary catheter. MRSA
has since been found to cause illness in the com-
munity outside of hospitals and other health facili-
ties. Community-associated MRSA infections
typically cause skin lesions (such as boils), but can
also cause severe illness. The transmission of MRSA
is largely from people with active MRSA skin infec-
tions. MRSA is almost always spread by direct phys-
ical contact, and not through the air. Just as S.
aureus can be carried on the skin or in the nose
without causing any disease, MRSA can be carried in
this way as well, a process known as colonization.
MRSA infections are usually mild superficial infec-
tions of the skin that can be treated successfully with
proper skin care and antibiotics. However, MRSA
can be difficult to treat and can progress to life-
threatening blood or bone infections because there
are fewer effective antibiotics available for treat-
ment.
methimazole
An antithyroid medication (brand
name: Tapazol) that is prescribed to treat hyperthy-
roidism. Also known as thiamazole.
methotrexate
An immune-suppressing drug
(brand names: Rheumatrex, Trexall) that is used to
treat rheumatoid arthritis, severe psoriasis, reactive
arthritis, and severe asthma. In high doses it is also
used as a part of cancer chemotherapy programs.
Methotrexate is an effective but potentially danger-
ous medication. People taking methotrexate must
have their lung, liver, and kidney function moni-
tored regularly, and they need blood testing to be
done frequently as well. Methotrexate interacts dan-
gerously, and potentially fatally, with many other
medications, including prescription and over-the-
counter nonsteroidal anti-inflammatory drugs, even
aspirin and ibuprofen. Folic acid supplements are
sometimes used to counteract side effects of
methotrexate. Methotrexate should be taken on an
empty stomach.
metrorrhagia
Uterine bleeding at irregular inter-
vals, particularly between periods. Metrorrhagia can
cause significant anemia. It may also be a sign of
underlying disease, such as hormone disorder, uter-
ine fibroids, or cancer of the uterus. See also
menometrorrhagia; menorrhagia.